We've been experimenting with homemade facepaint here recently. It all started because I was doing a theme about clowns with the kids I taught at school. I wanted them to experience having their face painted like clowns. There are quite a few allergies among the kids I teach so I didn't really want to purchase commercial facepaint as I wasn't sure what sort of 'extras' it would have in it.
This facepaint is what we came up with. It is made using a combination of sorbolene (we used a good quality sorbolene from the chemist which didn't contain any sort of 'extras'), cornflour, water and food colouring. It works well although it is quite thick. It also doesn't last long. As soon as it is dry it tends to flake off (although I personally prefer this to having to scrub faces to get facepaint off!)
1 tbsp sorbolene
2 tbsp water
6 tbsp cornflour
Mix sorbolene with water, gradually add cornflour (don't do this too quickly or else you will get a lumpy mixture). Add food colouring as desired.
That's it really - a simple, no-fuss way to make facepaint!